In a semiconductor processing apparatus that performs plasma etching on a substrate to be processed, such as a silicon wafer, the substrate is mounted on a mounting table installed at the center of a processing chamber. The mounting table generally has a structure in which an electrostatic chuck (hereinafter, referred to as an ‘ESC’) is provided at the top of a support made of a metal material exhibiting high thermal conductivity.
Generally, the electrostatic chuck has a stack structure including an insulating (dielectric) layer disposed at an uppermost portion of the electrostatic chuck, a film-shaped electrode, which is a conductive layer and is disposed below the insulating layer, and an insulating layer disposed below the film-shaped electrode. The insulating layer is generally made of alumina (Al2O3). An aluminum sheet, an aluminum foil, or an aluminum joint layer is generally used as the film-shaped electrode. The film-shaped electrode functions as a voltage application electrode to hold the wafer with an electrostatic force.
Also, in addition to the film-shaped electrode, a heat transfer layer made of a metal material may be provided at the ESC to render the temperature of the ESC uniform.
The film-shaped electrode and the heat transfer layer are metal layers made of an electrically conductive metal material. Both the film-shaped electrode and the heat transfer layer are exposed from a peripheral side surface of the ESC. When the ends of the metal layers are exposed from the peripheral side surface of the ESC, the metal layers may be corroded by, for example, a halogen-based corrosion gas used to manufacture semiconductors. Also, the corroded metal may cause contamination.
Also, when the film-shaped electrode is used as an electrode of the ESC, an electric discharge or an electric leakage to a metal body adjacent to the film-shaped electrode, e.g., a focus ring installed at a periphery of the ESC, may occur because a high voltage is applied to the film-shaped electrode.
Accordingly, an insulating ceramic material or alumina may be thermally sprayed on the peripheral side surface of the ESC from which the metal layers are exposed in order to prevent the occurrence of the above-mentioned problem.
For example, Patent Document 1 discloses a susceptor used in the manufacture of semiconductors and having a conductor and an insulating ceramic member, the susceptor being characterized in that a portion of the conductor exposed from the ceramic member is covered with a thermally sprayed insulating film.    [Patent Document 1] Japanese Patent Laid-open Application No. H06-279974
An electrostatic chuck generally has a stack structure including a conductive layer and insulating layers between which the conductive layer is interposed. When the conductive layer is exposed to the outside, an electric leakage from the conductive layer may occur, or a metal material of the conductive layer may be corroded by an atmosphere gas. Accordingly, a thermally sprayed film made of an insulating material, such as a ceramic material, is formed at the exposed portion of the conductive layer, i.e., the peripheral side surface of the electrostatic chuck, to cover the exposed portion of the metal layer. However, the thermally sprayed film formed for such purpose may be easily damaged.
FIGS. 5A to 5C illustrate examples of shapes of a thermally sprayed ceramic coating (thermally sprayed layer) formed at the peripheral side surface of an electrostatic chuck in a conventional technique. Generally, as shown in FIG. 5A, a flat thermally sprayed ceramic layer 6 is formed almost entirely at the peripheral side surface of an electrostatic chuck (ESC) 21 including a conductive layer 20. However, since the thermally sprayed ceramic layer 6 is soft, the thermally sprayed ceramic layer 6 may be easily damaged when an external impact is applied to the thermally sprayed ceramic layer 6 during handling, such as installation or separation, of the ESC.
The inventors of the present invention have examined effects of a thermal spraying method of changing a shape or a covering range of the thermally sprayed ceramic layer to prevent the thermally sprayed ceramic layer from being easily peeled off. As one example, as shown in FIG. 5B, the thermally sprayed ceramic layer 6 is extended horizontally from the top and bottom of the thermally sprayed ceramic layer 6 such that the thermally sprayed ceramic layer 6 is formed at the top and bottom of the upper and lower insulating layers as well as at the side of the ESC. As another example, as shown in FIG. 5C, the thermally sprayed ceramic layer 6 is extended only from the bottom of the thermally sprayed ceramic layer 6 such that the thermally sprayed ceramic layer 6 is formed at the bottom of the lower insulating layer as well as at the side of the ESC. The inventors have examined the effects of preventing the thermally sprayed ceramic layer from being peeled off when the thermally sprayed ceramic layer is formed in the above-mentioned shapes.
As a result, the peeling is efficiently prevented by increasing the adhesion area; however, corners of the thermally sprayed ceramic layer are damaged by an external impact since the thermally sprayed ceramic layer is thin and soft. Accordingly, it has been revealed that it is impossible to completely prevent the damage to the thermally sprayed ceramic layer due to an external impact although the thermally sprayed ceramic layer is formed in the shape shown in FIG. 5B or 5C.
Further, Patent Document 1 discloses a study on a method of forming the thermally sprayed ceramic film. Hereinafter, the method of forming the thermally sprayed ceramic film will be described with reference to FIGS. 6A and 6B. In an embodiment of the cited patent document, as shown in FIG. 6A, an upper part of the susceptor has a structure in which a film-shaped electrode 24 is interposed between a disc-shaped ceramic member 22 and a disc-shaped ceramic support 23.
Further, a thermally sprayed film (thermally sprayed layer) is formed as follows. First, as shown in FIG. 6A, a peripheral portion of the film-shaped electrode 24 is removed by etching, and an insulating ceramic material is sprayed into a groove 25 formed by removing the peripheral portion of the film-shaped electrode 24. During spraying, a thermally sprayed ceramic layer 6 is formed to fill the groove 25 and protrude from the sides of the upper and lower ceramic circular plates.
As a result, the thermally sprayed ceramic layer 6 filled in the groove 25 is formed to thereby improve adhesion between the disc-shaped ceramics and the thermally sprayed ceramic layer 6. However, the inventors have found that the thermally sprayed ceramic layer 6 has a protruding portion, which may easily collide with a surrounding object. It is known that, when the protruding portion of the thermally sprayed ceramic layer 6 collides with a surrounding rigid body, an external impact is applied to the thermally sprayed ceramic layer 6, and the thermally sprayed ceramic layer 6 is damaged and easily peeled off.
Further, in an etching process of the peripheral portion of the film-shaped electrode 24 as disclosed in Patent Document 1, the ceramic material is not sufficiently inserted into the processed portion. Accordingly, it is difficult to fully cover the metal layer. Also, since a contact area between the thermally sprayed ceramics and the processed portion is not sufficient, an adhesion strength between the thermally sprayed ceramics and the processed portion is poor and, thus, the thermally sprayed ceramics may be easily peeled off from the processed portion.